The present embodiments relate generally to data storage systems and more particularly, but not by way of limitation, to the collection of readback signal modulation data in a data storage system.
Mass storage devices are one of many components of modern computers. One type of mass storage device is a disc drive. In general, disc drives read and write information along concentric tracks formed on discs. A magnetic disc drive, which is a particular type of disc drive, includes one or more magnetic discs mounted for rotation on a hub or spindle. A typical magnetic disc drive also includes heads that communicate with the magnetic discs. Each head is carried by a slider which is designed to “fly” just over the surface of the rotating disc. An actuator moves the slider radially over the disc surface for track seek operations and holds the head directly over a track on the disc surface for track following operations.
Information is typically stored in concentric tracks on the surface of a magnetic disc by providing a write signal to the head to encode flux reversals on the surface of the magnetic disc representing the data to be stored. In retrieving data from the disc, the drive controller controls the actuator so that the head flies above the magnetic disc, sensing the flux reversals on the magnetic disc, and generating a readback signal based on those flux reversals. The readback signal is typically conditioned and then decoded by a drive read channel to recover data represented by flux reversals stored on the magnetic disc.
To locate a particular track on a disc, disc drives typically use embedded servo fields on the disc. Thus, a typical disc format comprises “pie-shaped” wedges of servo information interweaved between sections of data. The embedded servo fields are utilized by a servo sub-system to position a head over a particular track.
As the density of data recorded on magnetic discs continues to increase, it is becoming necessary for the spacing between the head carried by the slider and the disc to decrease to very small distances. Spacings of well below 10 nano-meters (nm) are required in some applications. In disc drive systems having such small slider-disc spacing, the possibility of contact between the slider and the disc is relatively high, due to factors such as slider manufacturing process limitations and limited air-bearing modeling capabilities. A promising method to detect such contacts is to examine modulation in a readback signal produced by the head during a read operation, for example. However, current disc drives are not configured for collection of readback signal modulation data that is suitable for use in providing relatively accurate slider-disc contact detection, for example.
The present embodiments address these problems and offers other advantages over the prior art.